By TEBAOFLEX Jyen. Originally published on November 22, 2025.
A medium-voltage cable on an STS, RTG or ARMG crane is part of an electrical and mechanical system. Selection must account for voltage, current, grounding, drum geometry, operating tension, acceleration, bending and the environment. A model name or maximum travel-speed figure does not establish suitability for a particular crane.
Define the duty before selecting a cable family
- Electrical supply: rated voltage, system earthing, operating and starting current, fault level and protection requirements.
- Motion: maximum speed, acceleration and deceleration, travel length, cycle rate and emergency-stop conditions.
- Reel arrangement: monospiral or multilayer cylindrical drum, minimum barrel diameter, cable guides, turnover arrangement and length remaining wound.
- Environment: ambient temperature, sunlight, water, oils, abrasion, mechanical impact and required inspection access.
- Communications: copper data pairs or optical fibers, transceivers, connectors, link budget and requirements during motion.
Published cable catalogues distinguish constructions and installation conditions. Prysmian’s PANZERFLEX installation guidance, for example, emphasizes suitable guide geometry and alignment with the cable payout plane to limit unwanted torsion. Apply the installation instructions for the exact selected cable and reel, rather than transferring limits from a different family.
Prysmian PANZERFLEX catalogue — handling and installation guidance
Speed is not a cable-tension calculation
For an unchanged effective mass, kinetic energy follows E = ½mv². Increasing speed from 60 to 240 m/min therefore multiplies that energy by 16. It does not by itself multiply cable tension by 16: tension also depends on acceleration, reel torque, inertia, friction, hanging length and the motion-control strategy.
Ask the equipment designer for operating and emergency-load cases. Compare them with the cable manufacturer’s allowable tension and the capacity of the complete anchoring system. Do not substitute breaking strength for working load, or apply a generic pretension percentage without a defined load basis.
Read the electrical construction as a complete design
For an MV reeling cable, obtain a drawing identifying the conductors, conductor screens, insulation, insulation screens, protective conductors, any metallic screens and mechanical reinforcement. Where a triple-extruded insulation system is specified, that manufacturing description is not evidence of a void-free cable or an automatic partial-discharge pass.
Conductor class and resistance must be specified for the actual material and size. IEC 60228 is a conductor standard; it does not certify the complete cable’s reeling speed, bend endurance or permissible pulling force.
IEC 60228:2023 — conductor requirements
Specify the required shielding and grounding arrangement separately from mechanical reinforcement. A monitoring screen can be part of a protection system, but the screen alone cannot guarantee interruption within 35 ms. Detection, relay settings, switching equipment, earthing and fault conditions must be assessed together by the responsible electrical designer.
Optical fibers in a moving MV cable
For a hybrid cable, record fiber type and count, termination details, optical budget and the mechanical qualification of the finished cable. Fiber grade alone does not demonstrate the cable’s dynamic bending, torsional or crush performance.
ITU-T G.657 specifies improved bending-loss performance relative to G.652 fibers. Although G.657 category A fibers are compatible with G.652.D, a G.652.D designation alone does not establish G.657.A2 performance. Specify the required grade explicitly and verify the supplier’s data for the cabled fiber.
ITU-T G.657 — bending-loss-insensitive single-mode fiber
Agree the optical test conditions for the finished assembly, including wavelengths, connector and splice losses, and any checks during or after the specified motion test. Do not infer a universal attenuation-change limit from a model name or an unverified diagram.
Account for the cable remaining wound on the reel
A free-air current rating cannot simply be assumed to apply to a wound cable. Establish the permitted current for the actual reel geometry, remaining wound length, ambient conditions, ventilation and duty cycle. Use cable- and reel-specific thermal data or an agreed engineering calculation; do not transfer a low-voltage table to an MV arrangement without confirming its scope.
Illustrative derating arithmetic — assumed factors only
The following example explains multiplication of correction factors. Assume a reference current of 245 A, an ambient factor of 0.87 and a winding factor of 0.65. These are hypothetical inputs, not verified ratings for an HVR-D cable and not universal DIN VDE 0298-4 factors.
For this illustration: current = reference current × assumed ambient factor × assumed winding factor.
245 × 0.87 × 0.65 = 138.5475 A, approximately 138.5 A.
If a separate hypothetical arrangement instead used a winding factor of 0.85, while the other assumptions remained unchanged:
245 × 0.87 × 0.85 = 181.1775 A, approximately 181.2 A. This is a 30.8% arithmetic increase relative to the first assumed result. It is not a promised gain from changing reel type. Neither value should be used for equipment sizing without validated inputs.
Installation and commissioning checks
- Confirm the manufacturer’s payout procedure, cable orientation and installation tension. Avoid adding twist during transfer from the shipping drum.
- Check drum and guide dimensions against the specified moving bend radius; distinguish bend radius from diameter and from spacing between reversing bends.
- Align guides with the payout route and inspect rollers for seizure, wear and damaging edges.
- Use the approved anchoring and strain-relief arrangement so operating pull is not transferred to MV terminations or optical connections.
- Have qualified personnel install MV accessories to their own instructions, including screen preparation, cleanliness and electrical clearances.
- Set inspection intervals from the equipment manufacturer’s guidance and site duty. Check reel control, drainage, contamination and cable damage; no universal 90-day interval is assumed.
Document the acceptance tests before purchase
A test plan must identify the ordered cable, applicable product specification and edition, test methods, acceptance limits and traceability to the supplied drum. The following is a checklist to agree with the supplier, not a report of measured TEBAOFLEX results.
- Construction, dimensional and conductor-resistance checks for the specified cable.
- Required voltage-withstand and partial-discharge tests with clearly stated voltage, duration, sensitivity and acceptance criterion.
- Mechanical qualification relevant to the intended bending, tension, torsion and reel duty.
- Optical continuity and loss records for hybrid cables, with agreed before/after-motion checks where applicable.
- Identification of routine, sample and type tests; test equipment calibration and drum-specific results where required.
IEC 60270:2025 addresses charge-based partial-discharge measurement, including measurement circuits, calibration and interference. It is not, on its own, a universal 5 pC acceptance specification for every MV reeling cable. The applicable cable specification and agreed test plan must supply the relevant test voltage and acceptance limit.
IEC 60270:2025 — charge-based partial-discharge measurement
Frequently asked questions
Does a cable designation prove its maximum reeling speed? No. Obtain the precise construction and operating limits, including how speed relates to acceleration, tension and guide geometry.
Must every high-speed crane use the same outer-sheath compound? No blanket requirement is established here. Specify the environmental and mechanical performance needed and verify the proposed compound and finished cable against those requirements.
Can an optical-fiber or monitoring-screen option be assumed from the family name? No. Confirm the exact drawing, fiber count, screen arrangement and compatible termination and protection systems.
Request a project-specific cable specification
Send the crane duty, cable route and equipment drawings to TEBAOFLEX for a project-specific specification. WhatsApp: +86 185 9591 3361. Request the applicable datasheet and documented test requirements before placing an order.